Offshore wind farms: How do they work? What are the benefits and disadvantages?

Offshore wind farms have become an increasingly popular topic of discussion among Western countries battling to curb their carbon emissions and reach their net zero goals. 

Building wind farms to generate power has been identified as a potential green solution. 

Jersey’s Environment Minister, Deputy Jonathan Renouf has put forward proposals to build a 1,000 MW wind farm off the island’s southwest coast. 

Mr Renouf said the facility could generate six times Jersey’s electricity needs, allowing excess power to be exported. 

However, wind power isn't without its controversies. 

What are offshore wind farms and how do they work?

Offshore wind farms are made up of wind turbines fixed to the sea floor.

The force of the wind spins the blades of the turbine and converts kinetic energy into electricity.

This electricity is transported through underwater cables to the coast.

Once it reaches electrical substations on the mainland it will be transformed to be able to be used in homes and businesses.

How much does wind currently contribute to the electrical mix?

Wind (onshore and offshore) made up an impressive 24% of the UK's electricity production last year.

In total, offshore wind farms in the UK generated 45 TWh of electricity last year, up from 37TWh in 2021.

What are the benefits of offshore windfarms? 

Offshore wind farms are less likely to be an eyesore than onshore ones. 

However, those built within 26 miles of the coastline might still be visible from the shore. 

Offshore wind farms are considered more efficient than onshore wind farms, due to higher wind speeds, greater consistency and lack of interference from buildings or hills. 

An average onshore wind turbine produces around 2.5 to 3 MW in comparison to the offshore average of 3.6 MW.

What are the cons of offshore wind farms? 

Wind speeds are expected to fall due to global warming. This phenomenon is known as global stilling. 

Projections by the IPCC show that rapidly rising temperatures in the Arctic are expected to weaken winds across the Northern Hemisphere, even if nations collectively reach net zero by 2050.

In the UK winds are expected to weaken by 3% by 2050, and by up to 10% by 2100, according to climate website Carbon Brief.

Wind farms can only generate electricity when the wind is blowing at sufficient strength to turn the turbines, so other power generators such as fossil fuels and other renewables are currently needed as a backup. 

The underwater noises from turbines can impact fauna and other marine life.

Above ground the turbines can kill birds, however, Ørsted has described the numbers impacted as 'negligible'.

Offshore wind farms are more expensive to build than onshore ones and are more challenging to maintain.

Which country currently produces the most offshore wind?

Last year the total worldwide offshore wind power gross capacity stood at 64.3 gigawatts.

China generated 49% of this, followed by the UK with 22% and Germany which produced 13% (Source: Global Wind Energy Council).

Are there any other plans in place to increase offshore wind generation across the Channel Islands, the UK and the US?

There are currently no offshore wind farms in the Channel Islands.

However, if the recent proposals to build a 1000 MW farm off of Jersey's southwest coast are given the green flag, laws allowing the development could be in place by the end of 2024 with a developer chosen in 2025.

The UK is already Europe’s largest market for offshore wind and has the largest installed capacity of offshore wind in the world with 10GW currently in operation.

The UK Government is planning to generate four times this amount by 2030.

The US is lagging behind the UK, China and most of Europe in its production of offshore wind energy.

But the Biden administration hopes to expand this sector, announcing an ambitious target of generating 30 GW of offshore wind by 2030.

Are there many challenges in the way to expanding offshore wind power?

The main challenge facing offshore wind developments is the distance from the shoreline to the farms.

Increasing the distance to the farms tends to generate more public support as they will not be as visible, but installation, operation and maintenance are more difficult to perform and lead to higher costs. 

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